x.] SOIL SURVEYS 389 



Soil Surveys. 



To render the scientific study of soils properly 

 available for the service of the agriculturalist, more is 

 required than the examination of single samples of 

 soil, representing, at the best, only the land dealt with 

 by one person. Over any wide district, not only would 

 such work become expensive and practically endless, 

 liable also to many sources of error through local 

 and accidental variations of the soil on the spot from 

 which the sample was drawn, but each analysis would 

 lose the greater part of its value if it could not be co- 

 ordinated and brought into line with others drawn from 

 soils of the same type. A general soil survey of a 

 district, so as to be able to lay down a plan of the 

 distribution of the various soil types, accompanied by 

 a discussion of the broad characteristics of each, 

 should be the basis upon which the interpretation of 

 the analysis of the soil of any particular field is to 

 be founded. Only by comparison with the type can 

 the analysis of any particular soil be properly inter- 

 preted — e.g., the fact that a soil from a given arable 

 field contains 015 per cent, of phosphoric acid takes 

 a very different aspect when it is known that the 

 soils of the same type contain as a rule 018 to 0-20 

 per cent, of phosphoric acid, particularly if, also, the 

 response of that kind of land to phosphatic manures is 

 known by field trials, or from the accumulated experience 

 of farmers. The first question which requires settle- 

 ment is how far a soil survey is possible; to what 

 extent can the boundaries of soil types be traced ; are 

 the various types sufficiently constant over a wide area 

 to render this mapping feasible ? In many cases there 

 seems to be little but confusion, even in the soils on a 

 single farm ; field differs from field, and great variations 



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